Encyclopedias are invaluable sources for detailed definitions, summary and background information.
Reading an encyclopedia article is a good way to get a grasp of the range and depth of the topic you are investigating. An encyclopedia article can also help you become familiar with the terminology and concepts relating to your topic.
Encyclopedia articles are usually written by expert subject specialists for beginners. This means that the information is reliable and authoritative, but you don't have to be an expert to understand it.
Articles in encyclopedias often conclude with a bibliography. These bibliographies are very useful for identifying additional sources of information on the topic.